The chiral synthesis of the nucleoside coformycin and its aglycone, an imidazo(4,5-d)-(1,3)-diazepine, is proposed. These derivatives are known and potential adenosine deaminase (ADA) inhibitors, respectively. An analog of the potent ADA inhibitor, erythro-9-(2-hydroxy-3-nonyl) adenine (ENHA) which combines the structural features of the aglycone of coformycin and the side-chain of ENHA is also proposed. A variety of 5-substituted imidazo (4,5-d)-(1,3) diazepines, e.g., amino, oxo, mercapto, methylmercapto, etc., will also be prepared. It is envisaged that these analogs could serve as potential ADA as well as guanine deaminase (guanase) inhibitors. The synthetic schemes, herein, represent a combination of chemical and microbial transformation methods. The latter area involves the preparation of optically active sulfoxides as synthetic chiral inducers, and the reduction of key prochiral synthons. The development of these compounds could lead to their use as potentiators of clinically useful anticancer drugs, e.g., ara-A. Biological evaluations as ADA and guanase inhibitors will be conducted at the laboratories of Professor Robert E. Parks, Jr., of Brown University.